The present invention relates to a system for controlling a wavelength of laser beam emitted by a signal light source for wavelength stability in the field of a wavelength division multiplexing (WDM) optical communication system.
Traditionally, a single-mode laser (e.g., distributed feedback (DFB) laser) may be employed as a signal light source for use with WDM system. In a dense WDM (commonly referred to as xe2x80x9cDWDMxe2x80x9d) system, any deviation of an output or lasing wavelength of the light source from a predetermined wavelength can lead to cross talks between adjacent optical channels in a such a manner as to deteriorate the optical signals. To avoid such a problem, there is a need for providing a system for effectively and efficiently adjusting the wavelength of the output laser light from the signal light source for wavelength stability.
The present invention provides a system for controlling a wavelength of laser light comprising:
a light-emitting device for outputting laser light; means for regulating a temperature of said light-emitting device;
a wavelength monitor for receiving the laser light transmitted from said light-emitting device through an optical filter, said optical filter having a periodic wavelength-transmissivity intensity curve;
a controlling unit for providing a control signal to control an current supplied to said temperature regulating means responsive to a output signal from said wavelength monitor; said control signal having a polarity; and
means for switching the polarity of said control signal.